1. Field of the Invention
The present invention relates to a heat storage material for air conditioning or for waste heat recovery which principally contains magnesium chloride hexahydrate, and more particularly to a heat storage material with which a nucleator is admixed so as to suppress supercooling.
2. Description of the Prior Art
Since magnesium chloride hexahydrate (MgCl.sub.2.6H.sub.2 O, melting point: 117.degree. C.) is inexpensive and has high latent heat, it is a hopeful substance as a heat storage material for air conditioning or for waste heat recovery. However, it causes a conspicuous phenomenon of supercooling during heat release and does not release the latent heat even when the temperature has become lower by about 25.degree. C. than its solidifying point.
In order to effectively utilize the magnesium chloride hexahydrate as a heat storage material by suppressing the supercooling thereof, heat storage materials doped with nucleators have been proposed. They are disclosed, for example, in U.S. Pat. No. 4,329,242 entitled "HYDRATED MG(NO.sub.3).sub.2 MGCL.sub.2 REVERSIBLE PHASE CHANGE COMPOSITIONS" and U.S. Pat. No. 4,338,208, entitled "HYDRATED MGCL.sub.2 REVERSIBLE PHASE CHANGE COMPOSITIONS". The heat storage materials disclosed here are doped with alkaline nucleators such as strontium hydroxide (Sr(OH).sub.2), calcium oxide (CaO), calcium hydroxide (Ca(OH).sub.2), barium oxide (BaO) and barium hydroxide (Ba(OH).sub.2). Since, however, the magnesium chloride, which is the principal component, is acid, the addition of the alkaline nucleators thereto results in decomposing the heat storage materials. In the course of service, accordingly, the heat storage materials become incapable of phase changes and become useless as such.